Embodiments of the subject matter disclosed herein generally relate to a mill, and more specifically to a cutting head for a mill used to perform a Z-axis plunging operation, and a method of using the mill to perform a plunge milling operation.
In the oil and gas industry, compressors are often used to pressurize oil or gas flowing through a pipeline. Some compressors incorporate an impeller blade having a relatively complex geometry which may provide a desired flow characteristic to the fluid in the compressor. In the manufacture of such blades, a milling machine can be used to create the desired geometry by translating a cutting head along an X-axis and a Y-axis while plunging the cutting head along the Z-axis. This is referred to as a Z-axis plunging operation or plunge milling.
FIG. 1A is a side view of a known high-speed steel (HSS) mill 100, and FIG. 1B is a frontal view of the known mill 100. The known mill 100 includes top cutting teeth 151 on a top surface of a cutting head 150, which is connected to a motor driven shaft extending along the Z-axis. Rotation of the cutting head 150 around the Z-axis results in the removal of material from a work piece, such as an impeller blade, by the top cutting teeth 151. FIG. 2 shows a known insert mill 102 having teeth 171 that are attached with screws to a shaft 173.
Using mills 100 and 102 to manufacture an impeller blade can provide some advantages compared to manufacturing the blade by other methods. For example, mills 100 and 102 can be used to manufacture geometries that would be difficult or impossible to manufacture by other methods. Further, the known mills 100 and 102 can remove a relative large volume of material in a relatively short period of time.
However, some disadvantages have developed with known mills. For example, whereas conventional impeller blades are often made of aluminum, today's impeller blade designers are increasingly calling for the incorporation of other materials, such as super alloys. Characteristics of these materials, such as hardness, ductility, malleability, etc., may be different from the characteristics of aluminum. Such differences may render known mills less effective. Moreover, increased demand for impeller blades has fueled a corresponding demand for even greater production speeds. Accordingly, what is needed is a mill which may provide more versatility in the spectrum of materials which may be milled therewith and which may also provide increased wear resistance and run times.